#!/usr/bin/python3
# -*- coding: utf-8 -*-

# @Time    : 2018/11/7 10:24
# @Author  : chester7cheng
# @Email   : 346835646@qq.com
# @File    : ListComprehension.py
# @Software: PyCharm


L1 = ['Hello', 'World', 18, 'Apple', None]

# L2 = [isinstance(s, str) ? s.lower() : s for s in L1]

L2 = [s.lower() for s in L1 if isinstance(s, str)]

print(L2)
if L2 == ['hello', 'world', 'apple']:
    print('测试通过!')
else:
    print('测试失败!')


# def find_min_max(l):
#     if len(l) > 0:
#         return min(l), max(l)
#     else:
#         return None, None
